Corrosion inhibitors and compositions containing the same



CORRGSHGN INHIBETORS AND COMPGSITHONS CGNTAWING THE SAME Albert R. Sahel, Munster, 1nd,, Eiiis K. Fields, Chicago, Ill., and Rohert'E. Karll, Hammond, Inch, assignors to Standard Oil Company, (.hicago, 1H,, 'a corporation of Indiana v No Drawing. Application-December 4, 1952, Serial No. 324,144

14 Claims. c1. 252-42.?

This invention relates to new compositions of matter which are elfective corrosion inhibitors and which are noncorrosive to silver, silver alloys and similar metal. More particularly, the invention pertains to lubricant compositions containing the new compositions of matter which are non-corrosive to such metals and inhibit the corrosion thereof by sulfur and/ or corrosive sulfur-containing compounds.

Advances in the design and construction of internal combustion engines to produce improved and more efiicient and economical engines have presented many problems in the lubrication of the modern internal combustion engine. To meet the increased severe demands upon en: gine lubricants, many types of lubricant additives have been developed to obtain certain desired characteristics thereof. Among the more efiective addition agents which have been developed for compounding with lubricants are many sulfur-containing organic compounds such as, by way of example, sulfurized terpenes, sulfurized hydrocarbon oils, vegetable oils or animal oils, xanthate esters, organic polysulfides, particularly polyalkyl polysulfides, metal salts of organo-substituted thioacids of phosphorus, metal salts of the reaction product of a phosphorus sulfide and a hydrocarbon such as, for example, polybutenes and other polyolefins and combinations of the foregoing.

Recent increased use of silver and similar metals in the construction of improved internal combustion engines has created new problems in the use of sulfur-containing additives in lubricants for such engines; the primary problem created being the corrosion of such silver parts of the engine by the sulfur-containing additives. While such corrosion can be eliminated by avoiding the use of sulfurcontaining additives in lubricants for such engines, this solution of the problem is accompanied by the loss of the highly desired beneficial effects of the additives of this type.

It is an object of the present invention to provide a noncorrosive composition of matter. Another object of the invention is to provide a composition non-corrosive to silver and similar metal. A still further object of the invention is to provide a composition which will inhibit the corrosion of silver and similar metal by sulfur and/ or organo sulfur-containing compounds. A still further object of the invention is to provide a lubricant composition which is non-corrosive. Still another object of the invention is to provide a lubricant composition containing an addition agent which will inhibit the corrosion of silver and similar metal by sulfur and/or organo sulfur-containing compounds. A further object of the invention is to provide a method of inhibiting the corrosion of silver and similar metal. Still another object of the invention is to provide a method of lubricating internal combustion engine s containing silver and similar metal parts and inhibiting the corrosion of such metals by lubricants which contain sulfur and/ or organo sulfur-containing compounds I mada e with t e P e ent in atiqn h new p tent r 2,749,311 *ii atented .lurle 5, 19156 2 resi e f ma e i s nt al qi hl 9r o -di sible reaction product of a mercaptamformicacid and 2,5- dimercapto'l', 3,4-thiadiazole; the reactants being employed respectively in the molar ratio of from about 1: 1: 1 to about 3+x:1+x:x, where x is at least 1 and can be as great as '10, or more. The reaction is carried out at temperatures of from about 30 F. to about 250 F. An acid catalyst, for example chlorine, anhydrous HCl, concentrated sulfuric acid, a metal chloride, such as for example, zinc chloride, cadmium chloride, etc., may be em.- ployed, and generally will allow lower reaction tempert Depending pon the tem r u es em o h reaction time may vary from about 2 hours to about 72 h u If d si d th react on an e car i p in the presence of a suitable solvent or diluent, such as for example, dioxane, ethylene glycol, dimethyl and diethyl others, diethylene glycol methyl and ethyl ethers, etc.

Any mercaptan can be employed in the reaction although an aliphatic or aromatic monoor poly-mercaptan containing from 1 to about 30 carbon atoms, and preferably from about 6 to about 20 carbon atoms, is preferred. Examples of suitable mercaptans are ethyl mercaptan, butyl mercaptan, hexyl mercaptan, .octyl mercaptan, nonyl mercaptan, dodecyl mercap tan, octadecyl mercaptan, thiophenol, etc.

The preparation of the above-described reaction product illustrated by the following examples which are given solely by Way of illustration.

EXAMPLE I A mixture of l mole 2,5:dimercaptor1,3,4-thiadiazole, 2 moles of formic acid and 4 moles of t-octyl mercaptan was reacted in an ice bath using anhydrous chlorine as a catalyst. The product was placed in a cold room at about 40 F. for about twelve hours, diluted with hexane, and washed with water. After distilling off the hexane from the washed product, a light yellow viscous product having a sulfur content of 28.9% and a nitrogen content of 3.6 was recovered.

EXAMPLE II One mole of 2,5-dimercapto-1,3,4-thiadiazole, dissolved in dioxane, was reacted with 2 moles of formic acid and 4 moles of t-dodecyl mercaptan at 60 C. for three hours in the presence of anhydrous HCl. The dioxane was distilled from the mixture and a light yellow viscous product, similar to that of Example I, was recovered upon cooling.

EXAMPLE III Gne mole of 2,5-dimercapto-1,3,4-thiadiazole, dissolved in dioxane, was reacted with 2 moles of formic acid and 4 moles t-dodecyl mercaptan in an ice bath for three hours in the presence of anhydrous chlorine as a catalyst. The mixture was then placed in a cold room at about 46 F. for seventy-two hours and then washed with water, and the diluent distilled off. A light yellow viscous product having a s fur nt nt f 1.3% and a n o n content of 9.1% was obtained.

EXAMPLE IV A mixture of 1 mole 2,5-dimercapto-1,3,4:thiadiazole, 2 moles t-dodecyl mercaptan and 1 mole formic acid was dissolved in dioxane, heated to 102 C and refluxed for three hours. Upon distilling off the dioxane a crystalline product separated from the mother liquor upon cooling.

EXAMPLE v- A mixture of 1 mole 2,5-dimercapto-1,3,4-thiadiazolc, 1 mole t-octyl mercaptan and 1 mole formic acid was reacted for one hour atice bath temperature (about 33 F.) using a small amount of chlorine as catalyst. The reaction mixture was then placed a gold room at about 40 F for twelve hours, then diluted with cold hexane to precipitate a crystalline product. The crystalline product after repeated washing with cold water and drying gave a negative test for mercaptan. The product had a molecular weight of 320 and analyzed carbon 42.2%, hydrogen 6.7%, sulfur 41.3% and nitrogen 9.2%. A product having the general Formula A below had a calculated molecular Weight of 306, a carbon content of 43.1%, a hydrogen content of 5.9%, a sulfur content of 41.8%, and a nitrogen content of 9.2%.

EXAMPLE VI A mixture of 30 grams (0.2 mole) of 2,5-dirnercapto- 1,3,4-thiadiazole, 136.8 cubic centimeters (0.8 mole) t-octyl mercaptan, and 15.1 cubic centimeters (0.4 mole) 98-100% formic acid was stirred at 105 C. for seventytwo hours, after which time the reaction mixture was cooled and diluted with 75 cubic centimeters benzene and 25 cubic centimeters hexane. The organic layer was separated, washed with 200 cubic centimeters water, dried over Drierite, filtered and stripped of solvent. The re covered product was a viscous yellow oil-soluble liquid which analyzed 50.0% carbon, 7.8% hydrogen, 33.8% sulfur and 7.5% nitrogen.

EXAMPLE VII A solution of 45 grams (0.3 mole) of 2-dimercapto- 1,3,4-thiadiazole, 44 cubic centimeters (0.26 mole) t-octyl mercaptan, and 11.3 cubic centimeters (0.3 mole) formic acid (98-100%) in 100 cc. dioxane was heated at 100 C. for six hours. A white hexane-insoluble precipitate formed upon cooling, was removed, and hexane-washed. The hexane was evaporated from the filtrate and from the residue, on cooling, was crystallized a white hexanesoluble product having a melting point of 7l74 C. Analysis of the product was as follows: Calculated for C11H17S4N2: S=41.6%; N=9.l8%. Found: S=40.4%; N=8.36%.

The structures of the products resulting from the reactions of 2,5-diaiercapto-l,3,4-thiadiazole, formic acid and a mercaptan have not been definitely determined. Considering the possible structures of the resultant reaction products, it is believed that when the above-named reactants are used respectively in the molar ratio of 1:1:1

when the reactants are used respectively in the molar ratio of 112:4, where R is an alkyl, aryl or alkaryl radical. By increasing the molar ratio of the reactants by one or more, polymers of B may be formed, which may have the structure:

where n is at least 1. When the reactants above named are reacted in the molar ratio 1:1:2 respectively, it is possible that the resultant product may have the structure:

(D) SR N- g H H H- s o\ C-SH R t s where R is as above defined.

The above-described reaction products are effective corrosion inhibitors, particularly with respect to silver and similar metals when used in combination with lubricant base oils, such as those obtained by the polymerization of hydrocarbons, such as olefin polymers, for example, polybutenes, polypropylene and mixtures thereof, etc., synthetic lubricating oils of the alkylene-oxide type, for example, the Ucon oils, marketed by Carbide and Carbon Corporation, as well as other synthetic oils, such as the polycarboxylic acid ester-type oils, such as the esters of adipic acid, maleic acid, sebacic acid, azelaic acid, etc. The herein-described reaction products are eifectively used in such lubricants in concentrations of from about 0.02% to about 10%, and preferably from about 0.25% to about 5%.

While the above-described reaction products can be suitably employed alone in combination with a base oil, they are usually used in combination with other lubricant addition agents which impart various desired characteristics to the base oil. Usually, these reaction products are used in conjunction with detergent-type additives, particularly those which contain sulfur or phosphorus and sulfur. Additives of this type are usually used in amounts of from about 0.002% to about 10%, and preferably from about 0.01% to about 5%. Among the phosphorus and sulfur-containing addition agents are the neutralized reaction products of a phosphorus sulfide and a hydrocarbon, an alcohol, and a ketone, an amine or an ester. Of the phosphorus sulfide reaction product additives, we prefer to employ the neutralized reaction products of a phosphorus sulfide, such as phosphorus pentasulfide, and a hydrocarbon of the type described in U. S. 2,316,082 issued to C. M. Loane et al April 6, 1943. As taught in this patent, the preferred hydrocarbon constituent of the reaction is a mono-olefin hydrocarbon polymer resulting from the polymerization of low molecular Weight monoolefin hydrocarbons, such as propylenes, butenes, amylenes or copolymers thereof. Such polymers may be obtained by the polymerization of mono-olefins of less than 6 carbon atoms in the presence of a catalyst, such as sulfuric acid, phosphoric acid, boron fluoride, aluminum chloride, or other similar halide catalysts of the Friedel-Crafts type.

The polymers employed are preferably mono-olefin polymers or mixtures of mono-olefin polymers and isomono-olefin polymers having molecular weights ranging from about 150 to about 50,000, or more and preferably from about 500 to about 10,000. Such polymers can be obtained, for example, by the polymerization in the liquid phase of a hydrocarbon mixture containing monoand isomono-olefins, such as butylene and isobutylene at a temperature of from about F. to about F., in the presence of a metal halide catalyst of the Friedel- Crafts type, such as for example, boron fluoride, aluminum chloride, and the like. In the preparation of these polymers, a hydrocarbon mixture containing isobutylenc, butylenes and butanes recovered from petroleum gases especially those gases produced in the cracking of petroleum oils, in the manufacture of gasoline can be used.

Another suitable polymer is that obtained by polymerizing in the liquid phase, a hydrocarbon mixture comprising substantially C3 hydrocarbons in the presence of an aluminum chloride-complex catalyst. The catalyst is preferably prepared by heating aluminum chloride with isooctane. The hydrocarbon mixture is introduced into the bottom of the reactor and passed upward through the catalyst layer, while a temperature of from about 50 F. to about F. is maintained in the reactor. The propane and other saturated gases pass through the catalyst, while the propylene is polymerized under these conditions. The propylene polymer can be fractionated to any desired molecular weight, preferably from about 500 to about 1000, or higher.

Other suitable polymers are those obtained by polymerizing a hydrocarbon mixture containing about 10% to about 25% isobutylene at a temperature of from about 1y noted and given ratings according to the following scale:

1Bright 2Stained 3Grey-black 4-Black, smooth 5Black, flaky After the visual inspection, the silver strip is immersed in a potassium cyanide solution at room temperature until the silver surface assumes its original bright or silver appearance. The silver strip is then washed successively with distilled water and acetone, air-dried and weighed.

The following lubricant compositions were subjected to the above test and the results obtained tabulated in Table I.

Sample A.Control (solvent-extracted SAE 30 oil 3.3% barium-containing neutralized reaction product of P285 and a polybutene of about 1000 molecular weight).

Sample B.--A 0.75% reaction product of Example II.

Sample C.-A 0.5% reaction product of Example I.

Sample D.A 0.75% reaction product of Example VI.

Table 1 Sample: Silver corrosion (wt. loss.Mg.) A 20-25 B 0/1 C O/l D O/ 1 Since a weight loss of 20 milligrams is allowable, the ability of the herein-described reaction products of this invention to inhibit silver corrosion is demonstrated by the above data.

The effectiveness of the herein-described thiadiazole reaction products in inhibiting corrosion toward copper and/ or lead-containing metals, such as for example, copper-lead appearance, is demonstrated by the data in Table II, obtained by subjecting lubricants containing the additive to the following test:

A copper-lead test specimen is lightly abraided with steel Wool, washed with naphtha, dried and weighed to the nearest milligram. The cleaned copper-lead test specimen is suspended in a steel beaker, cleaned with a hot tri-sodium phosphate solution, rinsed with water, acetone and dried, and 250 grams of the oil to be tested, together with 0.625 gram lead oxide and 50 grams of a 3035 meshsand charged to the beaker. The beaker is then placed in a bath or heating block and heated to a temperature of 300 F. (:2" F.) while the contents are stirred by means of a stirrer rotating at 750 R. P. M. The contents of the beaker are maintained at this temperature for twenty-four hours, after which the copperlead test specimen is removed, rinsed with naphtha, dried and weighed. The test specimen is then replaced in the beaker and an additional 0.375 gram of lead oxide added to the test oil. At the end of an additional twenty-four hours of test operation, the test specimen is again removed, rinsed and dried as before, and weighed. The test specimen is again placed in the beaker together with an additional 0.250 gram of lead oxide and the test continued for another twenty-four hours (seventy-two hours total). At the conclusion of this time, the test specimen is removed from the beaker, rinsed with naphtha, dried and weighed.

The loss in weight of the test specimen is recorded after each Weighing.

This test, known as the Sand Stirring Corrosion Test, is referred to hereinafter as S. S. C. T.

The data obtained when Samples A to D, above, were subjected to the foregoing test, are tabulated in Table II.

Since weight losses of 200 milligrams in 48 hours and 500 milligrams in '72 hours are allowable, the copper-lead corrosion inhibiting property of the herein-described reaction products is clearly demonstrated by the above data.

Under certain conditions it is desirable to use in lubricant compositions elemental sulfur or an organic sulfurcontaining compound of the type herein-above described either alone or in combination with other additives. Elfective lubricant compositions are obtained by the combination of the neutralized reaction products of a phosphorus sulfide and a hydrocarbon, as above described, with elemental sulfur, or an organic sulfur-containing compound, such as sulfurized mineral oils, sulfurized nondrying animal and vegetable oils, sulfurized olefins and olefin polymers, sulfurized sperm oil, etc., as described and claimed in U. S. Reissue 22,464 issued to C. D. Kelso et a1. April 4, 1944, or with sulfurized terpenes, for example, dipentene, as described and claimed in U. S. 2,422,585 issued to T. H. Rogers et al. June 17, 1947. While these compounds impart highly desired characteristics to lubricants, and effectively inhibit the corrosion of copper and/ or lead, they are corrosive to silver and similar metals, and for this reason, lubricants containing such addition agents fail to pass the above-described EMD test. In accordance with the present invention, however, the incorporation in such lubricant compositions of small amounts, namely from about 0.1% to about 10%, and preferably from about 0.25% to about 5% of the hereindescribed reaction products effectively inhibits the corrosiveness of the silver-corrosive compounds without impairing their other desired properties.

The ability of the herein-described reaction products to inhibit the silver corrosion tendency of active sulfurcontaining organic compounds is demonstrated by the following EMD data in Table III, obtained with the following compositions:

Sample A.--Control (solvent-extracted SAE 30 oil-{- 3.3% barium-containing neutralized reaction product of P2S5 and a polybutene of about 1000 molecular weight+ 0.75 sulfurized dipentene).

Sample B'.-A+0.2% product of Example 1.

Sample C.A+0.065% product of Example V.

Sample D'.-A+0.15% product of Example V.

Sample E'.A'+0.l0% product of Example VI.

Table 111 Sample: E. M. D. (w. loss in mg.) A

B 0/1 C 0/1 D' 0/1 E 2/1 tion with the use of the herein-described reaction products in combination with the one or more secondary additives in lubricant compositions, the invention is not restricted to such use since these derivatives find utility when used alone in various lubricant compositions or hydrocarbon oil compositions to impart improved and desired characteristics thereto. Thus, for example, these products may be used alone in hydrocarbon oils to inhibit the corrosion of such oils to silver or copper and/or lead-containing metals and also effectively inhibit the oxidation of hydrocarbon oils.

In addition to the aforementioned detergent-type additives and corrosion inhibitors, compositions containing the herein-described reaction products can contain other additives, such as anti-oxidants, pourpoint depressors, extreme pressure agents, anti-wear agents, V. I. improvers, etc.

While this invention has been described in connection with the use of the herein-described additives and lubricant compositions, their use is not limited thereto; but the same can be used in products other than lubricating oils, such as for example, fuel oils, insulating oils, greases, non-drying animal and vegetable oils, waxes, asphalts and any fuels for internal combustion engines, particularly where sulfur corrosion must be combatted.

Percentages given herein and in the appended claims are weight percentages unless otherwise stated.

Although the present invention has been described with reference to specific embodiments thereof, the invention is not to be considered as limited thereto but includes within its scope such modifications and variations as come within the spirit of the appended claims.

We claim:

1. A new composition of matter, the oil-soluble reaction product of a mercaptan, formic acid and 2,5-dimercapto-1,3,4-thiadiazole, said reactants being reacted in the molar ratio of from about 1:1:1, respectively to about 3+x: 1+x:x, where x is an integer from 1 to about 10, inclusive, respectively, at a temperature of from about 30 F. to about 250 F. said mercaptan having the general formula RSH in which R is an aliphatic hydrocarbon radical having from about 6 to about 30 carbon atoms.

2. A new composition of matter as described in claim 1 in which the mercaptan is tertiary-octyl mercaptan.

3. A new composition of matter as described in claim 1 in which the mercaptan is dodecyl mercaptan.

4. A new composition of matter; the oil-soluble reaction product of an aliphatic mercaptan, formic acid and 2,5-dirnercapto-1,3,4-thiadiazole, said reactants being reacted in the molar ratio of 1:1:1, respectively, at a temperature of from about 30 F. to about 250 F. said mercaptan having the general formula RSH in which R is an aliphatic hydrocarbon radical having from about 6 to about 30 carbon atoms.

5. A new composition of matter, the oil-soluble reaction product of an aliphatic mercaptan, formic acid, and 2,5-dimercapto-1,3,4-thiadiazole, said reactants being reacted in the molar ratio of 4:2: 1, respectively, at a temperature of from about 30 F. to about 250 F. said mercaptan having the general formula RSH in which R is an aliphatic hydrocarbon radical having from about 6 to about 30 carbon atoms.

6. A composition comprising a major proportion of an oil, and from about 0.02% to about 10% of the oilsoluble reaction product of a mercaptan, formic acid, and 2,5-dimercapto-1,3,4-thiadiazole, said reactants being reacted in the molar ratio of from about 1:1:1, respectively, to about 3+x:1+x:x, where x is an integer from 1 to about 10, inclusive, respectively, at a temperature of from about 30 F. to about 250 F. said mercaptan having the general formula RSH in which R is an aliphatic hydrocarbon radical having from about 6 to about 30 carbon atoms.

7. A composition as described in claim 6 in which the mercaptan is tertiary-octyl mercaptan.

8. A composition as described in claim 6 in which the mercaptan is dodecyl mercaptan.

9. A composition as described in claim 6 in which the reaction is carried out in the presence of an acid catalyst.

10. A composition comprising a major proportion of an oil, from about 0.001% to about 10%, of a sulfurcontaining organic compound normally corrosive to silver, and from about 0.02% to about 10% of the oilsoluble reaction product of a mercaptan, formic acid, and 2,5-dimercapto-1,3,4-thiadiazole, said reactants being reacted in the molar ratio of from about 11121, respectively, to about 3+x:1+x:x, where x is an integer from 1 to about 10, inclusive, respectively, at a temperature of from about 30 F. to about 250 F. said mercaptan having the general formula RSH in which R is an aliphatic hydrocarbon radical having from about 6 to about 30 carbon atoms.

11. A lubricant composition comprising a major proportion of a hydrocarbon lubricating oil, from about 0.001% to about 10% of a phosphorusand sulfur-containing detergent-type lubricant additive, and from about 0.02% to about 10% of the oil-soluble reaction product of an aliphatic mercaptan, formic acid and 2,5-dimercapto-1,3,4-thiadiazole, said reactants being reacted in the molar ratio of from about 1:1:1, respectively, to about 3+x:1+x:x, where x is at least 1, respectively, at a temperature of from about 30 F. to about 250 F. said mercaptan having the general formula RSH in which R is an aliphatic hydrocarbon radical having from about 6 to about 30 carbon atoms.

12. A lubricant composition as described in claim 11, in which the detergent-type additive is a neutralized reaction product of a phosphorus sulfide and a hydrocarbon.

13. A lubricant composition comprising a major proportion of a hydrocarbon lubricating oil, from about 0.001% to about 10% of a sulfurized terpene, from about 0.001% to about 10% of a neutralized reaction product of a phosphorus sulfide and a hydrocarbon, and from about 0.02% to about 10% of the oil-soluble reaction product of an aliphatic mercaptan, formic acid and 2,5- dimercapto-1,3,4-thiadiazole, said reactants being reacted in the molar ratio of 1:1:1 at a temperature of from 30 F. to about 250 F. said mercaptan having the gen eral formula RSH in which R is an aliphatic hydrocarbon radical having from about 6 to about 30 carbon atoms.

14. A lubricant composition comprising a major proportion of a hydrocarbon lubricating oil, from about 0.001% to about 10% of a sulfurized terpene, from about 0.001% to about 10% of a neutralized reaction product of a phosphorus sulfide and a hydrocarbon, and from about 0.02% to about 10% of the oil-soluble reaction product of an aliphatic mercaptan, formic acid and 2,5- dimercapto-1,3,4-thiadiazole, said reactants being reacted in the molar ratio of from about 4:211, respectively at a temperature of from about 30 F. to about 250 F. said mercaptan having the general formula RSH in which R is an aliphatic hydrocarbon radical having from about 6 to about 30 carbon atoms.

No references citedl 

1. A NEW COMPOSITION OF WATER, THE OIL-SOLUBLE REACTION PRODUCT OF A MERCAPTAN, FORMIC ACID AND 2,5-DIMERCAPTO-1,3,4-THIADIAZOLE, SAID REACTANTS BEING REACTED IN THE MOLAR RATIO OF FROM ABOUT 1:1:1, RESPECTIVELY TO ABOUT 3+X:1+X:X, WHERE X IS AN INTEGER FROM 1 TO ABOUT 10, INCLUSIVE, RESPECTIVELY, AT A TEMPERATURE OF FROM ABOUT 30* F. TO ABOUT 250* F. SAID MERCAPTAN HAVING THE GENERAL FORMULA RSH IN WHICH R IS AN ALIPHATIC HYDROCARBON RADICAL HAVING FROM ABOUT 6 TO ABOUT 30 CARBON ATOMS.
 10. A COMPOSITION COMPRISING A MAJOR PROPORTION OF AN OIL, FROM ABOUT 0.0001% TO ABOUT 10%, OF A SULFURCONTAINING ORGANIC COMPOUND NORMALLY CORROSIVE TO SILVER, AND FROM ABOUT 0.02% TO ABOUT 10% OF THE OILSOLUBLE REACTION PRODUCT OF A MERCAPTAN, FORMIC ACID, AND 2,5-DIMERCAPTO-1,3,4-THIADIAZOLE, SAID REACTANTS BEING REACTED IN THE MOLAR RATIO OF FROM ABOUT 1:1:1, RESPECTIVELY, TO ABOUT 3+X:1+X:X, WHERE X IS AN INTEGER FROM 1 TO ABOUT 10, INCLUSIVE, RESPECTIVELY, AT A TEMPERATURE OF FROM ABOUT 30* F. TO ABOUT 250* F. SAID MERCAPTAN HAVING THE GENERAL FORMULA RSH IN WHICH R IS AN ALIPHATIC HYDROCARBON RADICAL HAVING FROM ABOUT 6 TO ABOUT 30 CARBON ATOMS. 